The present invention relates in general to reusable launch vehicle systems and, in particular, to a booster or launch vehicle stage that can be recovered after use by controlled aerodynamic descent to a landing area.
The space industry is undergoing explosive growth in terms of the types and numbers of missions and systems being deployed. Through telecommunication satellites and the deployment of the international space station to future space tours and visits the use of launch facilities is being greatly expanded. For example, a number of satellite constellations for communication systems have been proposed or implemented. These constellations range from tens to hundreds of satellites. According to some estimates, the number of projected satellite launches in the next ten years alone will double the total number of satellites launched in the first forty years of space access. As a result of this activity, the capacity of existing launch facilities and launch vehicle construction facilities will be tested. It is apparent that efficient and lower cost operation of launch vehicles and launch facilities will be demanded.
Existing launch vehicles typically include one or more stages which function to boost a payload aboard the launch vehicle into space. Such stages are generally disposable. More specifically, when stages of launch vehicles, such as a first stage, are no longer needed, the stages are separated from the upper stage, if any, and the payload interconnected thereto and are allowed to fall back towards the ground or a body of water. If any portion of such a stage is reusable at all, substantial reconstruction is generally required. The disposable nature of launch vehicle stages can be an expensive
Reusable spacecraft and stage systems have been proposed or implemented for some time. For example, the shuttles of the United States space shuttle fleet are reusable after re-entry and controlled landing upon inspection and some refurbishment. However, in order to achieve the velocities necessary for orbital insertion, the shuttles must utilize strap-on booster engines that are jettisoned during the launch process at considerable expense. Some existing or proposed systems are intended to permit recovery of launch vehicle stages such as by employing parachutes to soften splash down or landing. However, such systems entail a risk of significant damage, require substantial reconstruction of the stage after recovery and/or have achieved little or no commercial acceptance. Other proposed systems have contemplated the use of wings or other aerodynamic elements for retrieving boosters or stages. However, such systems may require substantial structural enhancement in connection with certain stage/tank structures and, in any event, it is apparent that such proposed systems have generally not achieved commercial acceptance.
The present invention is directed to a launch vehicle stage adapted for controlled aerodynamic descent back to a recovery area such as a specified landing area and an associated method of use. The invention makes use of stable stage structure, such as composite or aluminum isogrid construction, to support flight elements with minimal added mass. Through controlled descent, the stage can be recovered with minimal damage, potentially allowing for reuse with only routine refurbishment rather than full reconstruction. Moreover, the stage can be returned close to the launch site to shorten turn-around times between flights. In this manner, overall launch costs may be reduced and the capacity of launch facilities may be enhanced. Moreover, existing launch vehicle construction and handling resources can be freed for new launch vehicle construction.
According to one aspect of the present invention, a launch vehicle stage is provided with control surfaces for controlled aerodynamic descent. The launch vehicle stage is used to propel a payload system, such as a shuttle satellite and/or other space vehicle, towards an upper atmosphere or space trajectory or orbit. The launch vehicle stage includes: a booster system such as a solid or liquid phase rocket booster; a number of control surfaces structurally interconnected to the booster system; and a separation system for selectively separating the launch vehicle stage from the payload system. The booster is preferably structurally stable. That is, the booster is preferably constructed such that its outer skin assembly can support longitudinal and transverse loads even in the absence of substantial internal pressurization The control surfaces preferably include surfaces for controlling roll, pitch and yaw and for providing lift. In one embodiment, the control surfaces include wings, a tail, elevons, and canards. One or more of the control surfaces may be deployable between a retracted position for launch mode operation and an extended position for controlled descent mode operation. The separation system may include conventional, pneumatic, hydraulic or pyrotechnic elements for separation of the stage from the payload system on command or at a predetermined time, elevation, velocity or the like.
According to another aspect of the present invention, a launch vehicle stage is adapted for controlled flight based on command signals. The stage includes: a booster system; control surfaces, structurally interconnected to the booster system, that are moveable to control a course of descent of the stage; and a control system, operatively associated with the control surfaces, for receiving control signals concerning a desired maneuver of the stage and controlling the control surfaces based on the control signals to implement the desired maneuver. The stage may operate autonomously or by remote control. In this regard, the control system may receive the control signals from an onboard processor or the like, or may received the signals via stage-to-ground (and vice versa) telemetry. In either case, the control signals may be based at least in part on inputs from on-board or other instruments regarding current positional coordinates, attitude, altitude, velocity or other parameters.
According to another aspect of the present invention, a launch vehicle stage includes controlled flight systems and landing gear for controlled descent to a landing strip at a selected location, preferably close to launch facilities. The stage includes a booster system, a controllable aerodynamic flight system, and landing gear such as retractable wheels for substantially horizontal runway landings. The controlled aerodynamic flight system preferably includes at least two wings for providing lift sufficient for coasting or more preferably, sustained flight from a point of separation to the landing area and control surfaces for guidance to the landing area. The landing gear preferably includes wheel assemblies defining at least three points for landing and rolling to a stop. In one embodiment, a forward wheel assembly is retracted into a nose structure and two rear wheel assemblies are retracted into a fuselage structure during launch mode operation. The wheel assemblies are then deployed and locked into a fully extended position for landing. Such runway landing avoids damage and additional refurbishment or reconstruction that might otherwise be required in connection with skid landings or splash downs.
According to a still further aspect of the present invention, a propulsion system is provided for powered flight descent and recovery of a launch vehicle stage. The stage includes a booster system, a controllable flight aerodynamic system, and a propulsion system. The propulsion system may include one or more rocket engines or air breathing engines such as jet engines. Preferably, one or more jet engines are employed, thereby avoiding control complications associated with sloshing of substantial masses of liquid propellants. Conventional jet engines, such as fighter jet engines, may be employed. It will be appreciated that the associated power assist is useful in extending the glide path, or more preferably allowing for sustained flight, to a desired landing location. Such powered descent has particular advantages for retrieving stages after separation at high separation points (e.g., where the first stage of a multiple stage launch provides a significant portion of the total launch velocity) and where it is necessary for the stage to return at a substantial distance back to the launch location.
A method for using a launch vehicle stage in accordance with the present invention includes the steps of: providing a stage including a booster system and a controlled aerodynamic descent system, where the booster system is structurally stable so as to support aerodynamic and other loads; operating the booster system to provide a thrust to an associated payload system during launch mode operation; separating the stage system from the payload system after launch mode operation; and, after separation, operating the controlled aerodynamic descent system to control a course of descent of the stage to a landing area. The step of operating the controlled aerodynamic descent system may include monitoring the descent of the stage, receiving control signals, and deploying control surfaces of the controlled aerodynamic descent system to implement desired maneuvers. The method may further include the steps of operating a propulsion system to propel the stage along a trajectory towards the landing area.